Strongyloidiasis is considered to be one of the most neglected tropical diseases, mainly due to the poor sensitivity of the available diagnostic tests and lack of precise data on the epidemiology and seroprevalence of the disease especially in the endemic countries. The disease is mainly caused by a pathogenic species Strongyloides stercoralis that infects humans percutaneously. This parasite has a world-wide distribution and it is more prevalent in tropical and subtropical regions when poor sanitary conditions exist. The global prevalence of the disease is underestimated, however about 100-350 million people are estimated to be infected worldwide, mostly among the poorest residing in the least-developed countries (Requena-Mendez A., et al., Curr Trop Med Rep, 1: 207-215 (2014)).
Although Strongyloides stercoralis is the main species infecting humans, there are two other species that infect humans, namely Strongyloides fuelleborni and Strongyloides kellyi, which are seen only in a few places in the world. The present application shall refer to this group as Strongyloides spp, including but not limited to the above species, and preferably Strongyloides stercoralis. 
The health consequences of S. stercoralis infections range from asymptomatic light infections to chronic symptomatic strongyloidiasis involving anything from mild gastrointestinal morbidity to severe life-threatening conditions (Olsen A., et al., Trans. R. Soc. Trop. Med. Hyg. 103: 967-972 (2009)). In immunocompetent persons, the infection usually remains undiagnosed and the parasite may persist in the human host for decades through the autoinfection cycle of the parasite. Meanwhile, in immunosuppressive conditions, autoinfection may dominate and become overwhelming, with parasites at different stages of development invading virtually every host organ and tissue, resulting in development of hyperinfection and disseminated strongyloidiasis with a mortality rate as high as 87% (Siddiqui A A., and Berk S L., Travel Medicine, 33: 1040-1047 (2001)). As in the United States, almost all deaths due to helminths result from S. stercoralis hyperinfection (Muennig P., et al., N Engl J Med, 340: 773-779 (1999)).
Humans are exposed to S. stercoralis infection through direct contact with contaminated soil during agricultural, domestic and recreational activities. There is no gold standard test to rule out the infection, however the mainstay of diagnostic testing relies on the demonstration of larval stages in faecal specimens (Ramanathan R., et al., The Journal of Infectious Diseases, 198: 44-451 (2008)). To date, there are three test kits available (i) :Bordier-ELISA {hacek over ( )}(Bordier Affinity products SA, Switzerland); (ii) :SciMedx Strongyloides serology microwell ELISA {hacek over ( )}(SciMedx Corporation, Denville, N.J., USA); and (iii) :InBios Strongy Detect IgG ELISA {hacek over ( )}(InBios International, Inc., Seattle, Wash., USA). The first two tests are based on a one-step sandwich format immunoassay for qualitative detection of IgG-antibodies to Strongyloides antigen. The kit by InBios International is a one-step sandwich format immunoassay for detection of IgG-antibodies to the Strongyloides recombinant NIE antigen (Anderson N W., et al., Clin. Vaccine Immunol., 21: 732-736 (2014)). However this kit is still in development stage, as stated in the companyš website. One major drawback of these three tests is the need for an enzyme immunoassay analyzer (EIA) to measure the optical density of the reaction samples, which is impractical for point-of care in many settings.
The application of immunological screening of a cDNA library in identifying species specific genes has been established by many researchers over the past 30 years.
With regard to detection of strongyloidiasis, studies related to the construction of a cDNA library for identification of genes expressed in the L3 stage were undertaken by Ravi and co-workers (Ravi V., et al., Mol. Biochem. Parasitol., 125: 73-81 (2002)). They found a promising candidate gene that encodes for a 31 kDa NIE-recombinant protein. The recombinant protein was first incorporated into an assay which uses a luciferase immunoprecipitation system (LIPS) (Requena-M¶indez A., et al., PLoS Negl. Trop. Dis., 7: e2002 (2013); (Ramanathan R., et al., The Journal of Infectious Diseases, 198: 44-451 (2008)). LIPS is a modified ELISA in which serum containing antigen specific antibodies can be identified by measuring light production and requires the use of a vacuum manifold, a microplate luminometer for determining the luminescence and a mathematical analysis to obtain a read-out. As mentioned above, InBios International Inc are developing an IgG-ELISA using the NIE recombinant protein.
Currently there are no simple, rapid and convenient diagnostic methods suitable for use in low-resource countries where strongyloidiasis is endemic that avoid the requirement for sophisticated equipment.
In light of the disadvantages of current methods of detecting strongyloidiasis, there is a need to develop new markers and improved tests for the disease that have high selectivity and specificity.